Surface controlled subsurface safety valve

ABSTRACT

A surface controlled subsurface safety valve is positioned in a well production tubing and an adjustable choke is installed in the surface production tubing. The safety valve is operated by the absolute pressure of the production fluids in the well tubing. The adjustable choke is controlled by a timer which periodically cycles the choke to reduce the flow area available for production of well fluids for a predetermined short period of time. The reduction in flow area causes a corresponding build up of pressure in the surface tubing which is transmitted down the well tubing to the subsurface valve. Biasing means urges the valve to its closed position while tubing pressure urges the valve to its open positions. During normal well flowing conditions the force of the tubing pressure is less than the force of the biasing means and the valve, while remaining fully open is moved by the biasing means towards its closed position. Such movement is retarded by a dash pot arrangement in the valve. Means are provided in the valve to bypass the dash pot and cause rapid closure of the valve when the valve has reached a predetermined point towards its closed position. Under normal operations before the valve reaches the point of rapid closure the tubing pressure force at the valve is increased substantially over the force of the biasing means and the valve is moved rapidly to its initial open position. The increase in tubing pressure at the valve results from reducing the flow area by means of the adjustable choke in the surface tubing.

nited States Patent [191 Hill Feb. 26, 1974 SURFACE (CONTROLLEDSUBSURFACE SAFETY VALVE Tom ll. Hill, Houston, Tex.

[73] Assignee: Esso Production Research Company,

Houston, Tex.

[22] Filed: Oct. 2, 1972 [21] Appl. No.: 294,399

[75] Inventor:

Primary Examiner-H. Hampton Hunter Attorney, Agent, or Firm-John S.Schneider [57] ABSTRACT A surface controlled subsurface safety valve ispositioned in a well production tubing and an adjustable choke isinstalled in the surface production tubing.

The safety valve is operated by the absolute pressure of the productionfluids in the well tubing. The adjustable choke is controlled by a timerwhich periodically cycles the choke to reduce the flow area availablefor production of well fluids for a predetermined short period of time.The reduction in flow area causes a corresponding build up of pressurein the surface tubing which is transmitted down the well tubing to thesubsurface valve. Biasing means urges the valve to its closed positionwhile tubing pressure urges the valve to its open positions. Duringnormal well flowing conditions the force of the tubing pressure is lessthan the force of the biasing means and the valve, while remaining fullyopen is moved by the biasing means towards its closed position. Suchmovement is retarded by a dash pot arrangement in the valve. Means areprovided in the valve to bypass the dash pot and cause rapid closure ofthe valve when the valve has reached a predetermined point towards itsclosed position. Under normal operations before the valve reaches thepoint of rapid closure the tubing pressure force at the valve isincreased substantially over the force of the biasing means and thevalve is moved rapidly to its initial open position. The increase intubing pressure at the valve results from reducing the flow area bymeans of the adjustable choke in the surface tubing.

17 Claims, 5 Drawing Figures PATENTEDFEBZBW 3; 794,1 1T2.

SHEEY 1 OF 2 TIMER CONTROL SURFACE CONTROLLED SUBSURFACE SAFETY VALVEBACKGROUND OF THE INVENTION The present invention concerns a subsurfacesafety valve for controlling the flow of well fluids, particularly oiland/or gas produced from subsurface formations.

Surface controlled subsurface safety valves offer advantages overvelocity actuated safety valves. These advantages include in-placetestability, capacity production, and positive control from the surface.However, despite its advantages over velocity actuated safety valves thecommon hydraulic surface controlled valve, in which hydraulic operatingfluid is supplied to a subsurface valve from the surface throughexterior small diameter tubing or concentric larger diameter pipe, alsohas a disadvantage in its use in that such a valve cannot beeconomically installed on many existing well completions because thewell tubing may be cemented in place or be otherwise unmovable exceptthrough costly and high risk means. The present valve does not requirean exterior small diameter tubing or concentric larger diameter pipe ormovement of the well tubing and therefore overcomes the inherentdisadvantages in the hydraulic surface controlled valve.

SUMMARY OF THE INVENTION Briefly, the apparatus of the inventioncomprises a subsurface safety valve for use in controlling flow of wellfluids through well tubing or pipe and includes a valve housing and aflow tube arranged in the valve housing. The flow tube is movablebetween a first position in which well fluids are prevented from flowingthrough the flow tube and well tubing and a second position in which thewell fluids are permitted to flow through the flow tube and well tubing.The valve also includes biasing means for urging the flow tube to itsfirst position as well as means for retarding movement of the flow tubein its movement toward the first position thereof. The absolute pressureof the well fluids in the well tubing acts on the flow tube to move theflow tube, the flow tube being moved towards its second position againstthe bias of the biasing means when the absolute pressure of the wellfluids exceeds a predetermined amount. Periodically, the flow of wellfluids is choked momentarily at the surface by means of a timeadjustable choke which causes a pressure pulse to travel down the welltubing to the valve. The pressure pulse is at least equal to thepredetermined absolute pressure necessary to move the flow tube to itssecond position. The adjustable choke is timed to permit the flow tubeto move slowly from its second position towards its first position for aselected period of time. Then, before the flow tube reaches its firstposition the flow tube is returned to its second position under normaloperations. The valve will close if the pressure pulse is not sent fromthe adjustable choke to the valve. After the valve is closed it can bereopened by increasing the well tubing pressure in amounts sufficient toovercome the bias of the biasing means and move the flow tube from itsfirst position to its second position. The pulsing cycles are thenrepeated and the flow of fluids through the well tubing is unimpededduring normal operations.

In the operation of the subsurface valve of the present invention theflow of fluids from the well tubing is periodically reduced momentarilyat the surface to cause a pressure pulse to travel down the well tubingfrom the surface to the subsurface valve. The increased absolutepressure at the valve resulting from the pressure pulse forces the valveto a fully open position. Under normal flow conditions the force of theabsolute pressure at the valve is less than the force of biasing meanstending to close the valve. Thus the valve moves towards closure undernormal flow conditions while remaining fully open for a selected timeperiod. Prior to closure of the valve the increased absolute pressure atthe valve caused by reducing the flow of fluids at the surface causesthe valve to reset to its initial open position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a subsurface safetyvalve in accordance with the invention arranged in a well tubingsuspended in a well casing;

FIG. 2 shows the safety valve of FIG. 1 in open position;

FIG. 3 shows the safety valve of FIG. I in fully closed position; and

FIGS. 4 and 5 illustrate typical flowing pressure gradient curves.

DETAILED DESCRIPTION OF 'THE INVENTION There is shown in FIG. I a wellcasing in which a well pipe or tubing string 11 is suspended. A packerl2 closes the annulus between the casing and tubing string. Thedirectional flow of well fluids from a subsurface producing formation isindicated by the arrowed lines. A safety valve 13 is arranged in tubing11. An adjustable choke 14 is connected to tubing 11 at the surface anda suitable timer control 15 controls the operation of choke 14.

In FIG. 2 details of valve 13 are shown. A valve housing contains avalve seat 211 and an opening 22 in which is positioned a valve 22a. Thelower end of flow tube 25 contains openings 26 and a valve seatingsurface 27. In the valves closed position as seen in FIG. 3 surface 27has engaged valve seat 21 and openings 26 in the flow tube arepositioned within housing 20. Flow tube 25 is provided with an outwardlyextending upper shoulder piston 30 and an outwardly extending lowershoulder piston 31. These shoulders together with inner wall of housing20 form three chambers, 35, 36 and 37, isolated from each other by seals40 which engage the inner wall of housing 20. Upper seal 41 on the innerwall of housing 20 above chamber and lower seal 41 on the inner wall ofhousing 20 below chamber 37 are balanced seals. They engage the outerwall of flow tube 25 and prevent fluids from flowing between flow tube25 and the inner wall of housing 20 at those points. Lower chamber 37contains a spring 45 which acts against shoulder 31 to urge or bias flowtube 25 upwardly towards the closed position of the valve. Shoulder 31may be provided with a passage 46 which extends from the inner wall offlow tube 25 to the outer wall thereof between seals located on shoulder31. The valve 22a, arranged in the opening 22, is used to charge chamber30 with and retain in chamber 30 nitrogen or other gas. Chamber 36 iscompletely filled with a suitable hydraulic fluid as indicated. Theouter wall of flow tube 25 is formed to provide an annular recess 47 apredetermined distance below shoulder piston 30. An annular shoulder 48is provided on the inner wall of housing 20. Shoulder 48 contains asmall sized orifice 49 and a large fluid return bypass 50 on one end ofwhich is positioned a flexible check valve flapper 51. A seal 52 ispositioned on the inner wall of shoulder 48 and engages the unrecessedportion of the outer wall of flow tube 25. An opening 55 in flow tube 25is covered with sintered metal or other filter and fluidly communicateschamber 35 and the interior of flow tube 25.

Typical flowing pressure gradient curves are shown in FIGS. 4 and 5. InFIG. 4 the flowing pressure at an assumed valve depth of 3,000 feet fora gas-oil ratio (GOR) of 600 is 540 psig as indicated at 60. In FIG. 5at 3,000 feet and a GOR of 600 the flowing pressure is 1,190 psig asindicated at 61. Thus, when the producing rate is reduced from 300barrels per day to 400 barrels per day the surface tubing pressureincreases to 400 psig and the pressure at 3,000 feet depth increases tol,l90 psig. A 200 psig pressure change at the surface results in a 650psi pressure change at 3,000 feet. These flowing pressure gradientcurves are for stabilized conditions and do not reflect the timerequired to achieve the pressure changes.

In operation, referring in particular to FIG. 2 and using the pressurecurve examples given above flow tube 25 is biased upwardly by spring 45and, if used, nitrogen pressure, acting with an upward force on shoulder31 to bias the valve toward its closed position. The valve is operableby spring force alone however addition of the nitrogen charge increasesflexibility. Flow tube 25 is biased downwardly by the force of tubingfluid pressure acting with a downward force on piston shoulder 30 inchamber 35 to bias the valve open. Chamber 35 is in fluid communicationwith tubing pressure within flow tube 25 through the sintered metal orother filter covered opening 55. The valve closes when seating surface27 engages valve seat 21 as shown in FIG. 3.

During normal flowing conditions the force exerted by for example 540psig tubing pressure is less than the force acting upwardly on shoulderpiston 31 caused by spring 45 alone or together with a gas charge inchamber 37 and the valve is consequently attempting to close by movementof flow tube 25 upwardly as indicated in FIG. 2. Closure of the valve isslowed or retarded however by the hydraulic fluid in chamber 36 which isforced to pass through the small sized orifice 39 in shoulder 48 whileseal 52 engages the outer wall of flow tube 25. After the flow tube hasmoved a perdetermined distance towards closure, the recess 47 on theouter wall of flow tube 25 moves into position adjacent seal 52permitting the hydraulic fluid to bypass the small sized orifice 49 andcause rapid upward movement of flow tube 25 and thereby rapid closure ofthe valve. However, before recess 47 reaches seal 52 to permit fluid tobypass the small sized orifice 49 the pressure at the safety valve hasincreased to 1,190 psig tubing pressure through prior operation of thetimer and decreasing the size of adjustable choke 14. The pressure pulsepasses through opening 55 into chamber 35 and acts on shoulder piston 30to force flow tube 25 downwardly to its initial position. In moving theflow tube downwardly hydraulic fluid in chamber 36 bypasses small sizedorifice 49 and flows through large fluid return bypass 50 and flappervalve 51 which results in rapid resetting of flow tube 25 and the safetyvalve. The tubing pressure is cycled continuously to allow continuousproduction of fluids through flow tube 25 without interruption undernormal operations. When it is necessary or desirable to close the safetyvalve the timer does not operate the adjustable choke to reduce the sizethereof and flow tube 25 moves upwardly to engage the valve seatingsurfaces as shown in FIG. 3.

Timer 15, choke l4 and the control apparatus for controlling choke 14are commercially available components. For example, the choke mightsuitably be a diaphragm-type valve which is spring-opened and fluidpressure closable. The timer may suitably be an electric or mechanicalclock mechanism which energized a solenoid valve at preselected times.The solenoid valve opens at such times to permit a gas pressure tooperate the choke to reduce choke size a preselected amount momentarily.

Changes and modifications may be made in the illustrative embodiments ofthe invention shown and described herein without departing from thescope of the invention as defined in the appended claims.

Having fully described the nature, objects, apparatus, method andadvantages of my invention I claim:

1. A subsurface safety valve for use in closing off flow of well fluidsthrough well tubing comprising:

a valve housing;

a flow tube arranged in said valve housing and movable between a firstposition in which well fluids are prevented from flowing through saidflow tube and a second position in which well fluids are permitted toflow through said flow tube;

biasing means for urging said flow tube to its first position;

means for retarding movement of said flow tube from its second towardsits first position; and

said flow tube including means permitting the absolute pressure of saidwell fluids to act on said flow tube to move said flow tube, said flowtube being moved towards its second position against the bias of saidbiasing means when said absolute pressure exceeds a predeterminedamount, said absolute pressure exceeding said predetermined amountperiodically during movement of said flow tube towards its firstposition.

2. A subsurface safety valve as recited in claim 1 in which when saidflow tube reaches a third position between said second position and saidfirst position, in its travel from its second towards its firstposition, said flow tube is returned to its second position.

3. A subsurface safety valve as recited in claim 2 including first,second and third chambers formed between said flow tube and said valvehousing, said biasing means being arranged in said first chamber, saidmeans for retarding movement of said flow tube being located in saidsecond chamber and said means permitting the absolute pressure of saidwell fluids to act on said flow tube including an opening in said flowtube fluidly communicating said well fluid pressure and said thirdchamber.

4. A subsurface safety valve as recited in claim 3 in which two spacedapart shoulders extend from said flow tube to engage the inner wall ofsaid valve housing to form together with the inner wall of said valvehousing said first, second and third chambers, said second chambercontaining hydraulic fluid and orifice means for restricting movement ofsaid hydraulic fluid as said flow tube moves from its second to itsthird position.

5. A subsurface safety valve as recited in claim 4 in which said biasingmeans includes a spring.

6. A subsurface safety valve as recited in claim 5 in which said biasingmeans includes a spring and gas under pressure.

7. A subsurface safety valve as recited in claim 6 in which said flowtube includes an additional opening adjacent one end thereof and sealingmeans also adjacent said one end adapted to seal with said housing, saidadditional opening being sealed off within said housing by said sealingmeans engaging said housing to close off flow of well fluids throughsaid flow tube when said flow tube is in its first position, saidadditional opening fluidly communicating said well fluids and theinterior of said flow tube when said flow tube is in positions otherthan said first position thereof.

8. A subsurface safety valve as recited in claim 7 including meansarranged in said second chamber to permit said flow tube to move rapidlytowards its first position after it has reached its third position, andmeans in said second chamber permitting said flow tube to move rapidlytowards its second position in response to well fluid pressure.

9. A subsurface safety valve system for use in closing off flow of wellfluids through well tubing comprising:

a valve housing;

a flow tube arranged in said valve housing and movable between a firstposition in which well fluids are prevented from flowing through saidflow tube and a second position in which well fluids are permitted toflow through said flow tube;

biasing means for urging said flow tube to its first position;

means for retarding movement of said flow tube from its second towardsits first position;

said flow tube including means permitting the absolute pressure of saidwell fluids to act on said flow tube to move said flow tube, said flowtube being moved towards its second position against the bias of saidbiasing means when said absolute pressure exceeds a predeterminedamount, said absolute pressure exceeding said predetermined amountperiodically during movement of said flow tube towards its firstposition; and

a surface choke arranged in said surface tubing adapted to beperiodically closed to reduce the flow of well fluids therethrough andthereby increasing absolute pressure of the well fluids at thesubsurface valve.

10. A subsurface safety valve system as recited in claim 9 in which whensaid flow tube reaches a third position between said second and firstpositions said flow tube is returned to its second position.

11. A subsurface safety valve system as recited in claim 10 includingfirst, second and third chambers formed between said flow tube and saidvalve housing, said biasing means being arranged in said first chamber,said means for retarding movement of said flow tube being located insaid second chamber, and said means permitting the absolute pressure ofsaid well fluids to act on said flow tube including an opening in saidflow tube fluidly communicating said well fluid pressure and said thirdchamber.

12. A subsurface safety valve system as recited in claim 11 includingtwo spaced apart shoulders extending from the outer wall of said flowtube to the inner wall of said valve housing forming with the inner wallof said valve housing said first, second and third chambers, said secondchamber containing hydraulic fluid and orifice means for restrictingmovement of said flow tube from said second to said third positionthereof.

13. A subsurface safety valve system as recited in claim 12 in whichsaid biasing means includes a spring.

14. A subsurface safety valve system as recited in claim 13 in whichsaid biasing means includes a spring and pressurized gas.

15. A subsurface safety valve system as recited in claim 14in which saidflow tube includes an additional opening adjacent one end thereof andsealing means also adjacent said one end adapted to seal with saidhousing, said additional openings being sealed off within said housingby said sealing means engaging said housing to close off flow of wellfluids through said flow tube when said flow tube is in its firstposition, said additional opening fluidly communicating said well fluidsand the interior of said flow tube when said flow tube is in positionsother than said first position thereof.

16. A subsurface safety valve system as recited in claim 15 includingmeans arranged in said second chamber to permit said flow tube to moverapidly towards its first position from its third position, and means insaid second chamber permitting said flow tube to move rapidly towardsits second position in response to well fuid pressure.

17. A subsurface safety valve system as recited in claim 16 includingtimer means connected to said surface choke for periodically chokingsaid surface choke to increase absolute pressure within said welltubing.

1. A subsurface safety valve for use in closing off flow of well fluidsthrough well tubing comprising: a valve housing; a flow tube arranged insaid valve housing and movable between a first position in which wellfluids are prevented from flowing through said flow tube and a secondposition in which well fluids are permitted to flow through said flowtube; biasing means for urging said flow tube to its first position;means for retarding movement of said flow tube from its second towardsits first position; and said flow tube including means permitting theabsolute pressure of said well fluids to act on said flow tube to movesaid flow tube, said flow tube being moved towards its second positionagainst the bias of said biasing means when said absolute pressureexceeds a predetermined amount, said absolute pressure exceeding saidpredetermined amount periodically during movement of said flow tubetowards its first position.
 2. A subsurface safety valve as recited inclaim 1 in which when said flow tube reaches a third position betweensaid second position and said first position, in its travel from itssecond towards its first position, said flow tube is returned to itssecond position.
 3. A subsurface safety valve as recited in claim 2including first, second and third chambers formed between said flow tubeand said valve housing, said biasing means being arranged in said firstchamber, said means for retarding movement of said flow tube beinglocated in said second chamber and said means permitting the absolutepressure of said well fluids to act on said flow tube including anopening in said flow tube fluidly communicating said well fluid pressureand said third chamber.
 4. A subsurface safety valve as recited in claim3 in which two spaced apart shoulders extend from said flow tube toengage the inner wall of said valve housing to form together with theinner wall of said valve housing said first, second and third chambers,said second chamber containing hydraulic fluid and orifice means forrestricting movement of said hydraulic fluid as said flow tube movesfrom its second to its third position.
 5. A subsurface safety valve asrecited in claim 4 in which said biasing means includes a spring.
 6. Asubsurface safety valve as recited in claim 5 in which said biasingmeans includes a spring and gas under pressure.
 7. A subsurface safetyvalve as recited in claim 6 in which said flow tube includes anadditional opening adjacent one end thereof and sealing means alsoadjacent said one end adapted to seal with said housing, said additionalopeninG being sealed off within said housing by said sealing meansengaging said housing to close off flow of well fluids through said flowtube when said flow tube is in its first position, said additionalopening fluidly communicating said well fluids and the interior of saidflow tube when said flow tube is in positions other than said firstposition thereof.
 8. A subsurface safety valve as recited in claim 7including means arranged in said second chamber to permit said flow tubeto move rapidly towards its first position after it has reached itsthird position, and means in said second chamber permitting said flowtube to move rapidly towards its second position in response to wellfluid pressure.
 9. A subsurface safety valve system for use in closingoff flow of well fluids through well tubing comprising: a valve housing;a flow tube arranged in said valve housing and movable between a firstposition in which well fluids are prevented from flowing through saidflow tube and a second position in which well fluids are permitted toflow through said flow tube; biasing means for urging said flow tube toits first position; means for retarding movement of said flow tube fromits second towards its first position; said flow tube including meanspermitting the absolute pressure of said well fluids to act on said flowtube to move said flow tube, said flow tube being moved towards itssecond position against the bias of said biasing means when saidabsolute pressure exceeds a predetermined amount, said absolute pressureexceeding said predetermined amount periodically during movement of saidflow tube towards its first position; and a surface choke arranged insaid surface tubing adapted to be periodically closed to reduce the flowof well fluids therethrough and thereby increasing absolute pressure ofthe well fluids at the subsurface valve.
 10. A subsurface safety valvesystem as recited in claim 9 in which when said flow tube reaches athird position between said second and first positions said flow tube isreturned to its second position.
 11. A subsurface safety valve system asrecited in claim 10 including first, second and third chambers formedbetween said flow tube and said valve housing, said biasing means beingarranged in said first chamber, said means for retarding movement ofsaid flow tube being located in said second chamber, and said meanspermitting the absolute pressure of said well fluids to act on said flowtube including an opening in said flow tube fluidly communicating saidwell fluid pressure and said third chamber.
 12. A subsurface safetyvalve system as recited in claim 11 including two spaced apart shouldersextending from the outer wall of said flow tube to the inner wall ofsaid valve housing forming with the inner wall of said valve housingsaid first, second and third chambers, said second chamber containinghydraulic fluid and orifice means for restricting movement of said flowtube from said second to said third position thereof.
 13. A subsurfacesafety valve system as recited in claim 12 in which said biasing meansincludes a spring.
 14. A subsurface safety valve system as recited inclaim 13 in which said biasing means includes a spring and pressurizedgas.
 15. A subsurface safety valve system as recited in claim 14 inwhich said flow tube includes an additional opening adjacent one endthereof and sealing means also adjacent said one end adapted to sealwith said housing, said additional openings being sealed off within saidhousing by said sealing means engaging said housing to close off flow ofwell fluids through said flow tube when said flow tube is in its firstposition, said additional opening fluidly communicating said well fluidsand the interior of said flow tube when said flow tube is in positionsother than said first position thereof.
 16. A subsurface safety valvesystem as recited in claim 15 including means arranged in said secondchamber to permit said flow tube to move rapidlY towards its firstposition from its third position, and means in said second chamberpermitting said flow tube to move rapidly towards its second position inresponse to well fuid pressure.
 17. A subsurface safety valve system asrecited in claim 16 including timer means connected to said surfacechoke for periodically choking said surface choke to increase absolutepressure within said well tubing.